Circular stapler with controlled tissue compression

ABSTRACT

There are provided torque limiting mechanisms for use in tissue clamping surgical instruments. The torque limiting mechanisms generally include a driven member, engageable with an approximating mechanism of the surgical instruments, and having a driven surface and a driving member having a driving surface engageable with the driven surface of the driven member. The driving member is rotatable relative to the driven member such that the driving surface of the driving member slips relative to or disengages from the driven surface of the driven member at a predetermined engagement pressure.

BACKGROUND

1. Technical Field

The present disclosure relates to a force limiting mechanism for usewith surgical instruments incorporating tissue clamping structure. Moreparticularly, the present disclosure relates to tissue compressionlimiting mechanisms for use in surgical stapling instruments.

2. Background of Related Art

Anastomosis is the surgical joining of separate hollow organ sections.Typically, an anastomosis procedure follows surgery in which a diseasedor defective section of hollow tissue is removed and the remaining endsections are to be joined. Depending on the desired anastomosisprocedure, the end sections may be joined by either circular,end-to-side or side-to-side organ reconstruction methods.

In a circular anastomosis procedure, the two ends of the organ sectionsare joined by means of a stapling instrument which drives a circulararray of staples through the end section of each organ section andsimultaneously cores any tissue interior of the driven circular array ofstaples to free the tubular passage. Examples of instruments forperforming circular anastomosis of hollow organs are described in U.S.Pat. Nos. 7,303,106, 6,053,390, 5,588,579, 5,119,983, 5,005,749,4,646,745, 4,576,167 and 4,473,077, each of which is incorporated hereinin its entirety by reference. Typically, these instruments include anelongated shaft having a handle portion at a proximal end to actuate theinstrument and a staple holding component disposed at a distal end. Ananvil assembly including an anvil rod with attached anvil head ismounted to the distal end adjacent the staple holding component.Opposing end portions of tissue of the organs to be stapled are clampedbetween the anvil head and the staple holding component. The clampedtissue is stapled by driving a plurality of staples from the stapleholding component so that the ends of the staples pass through thetissue and are deformed by the anvil head.

In use, the staple holding component and anvil assembly are positionedwithin opposed tissue sections of the organs to be joined and areapproximated to pull the opposed tissue sections into position forstapling. This compresses the opposed tissues sections together. Currentdevices rely upon the operator to compress the tissue sections until theinstrument reaches a set approximation. If reaching the setapproximation compresses the tissue excessively then tissue damage orrestricted blood flow may lead to tissue necrosis. If the tissue is notclamped with sufficient compression, there is a greater propensity forbleeding and/or leaks at the anastomotic joint.

Therefore, there exists a need for a surgical stapler with a compressionlimiting mechanism to prevent excessive tissue compression. Therefurther exists a need for a surgical stapling instrument having a userselectable compression limiting mechanism to allow the user to preselectthe amount of compression applied to the tissue sections.

SUMMARY

There is provided a force or torque limiting mechanism for use in asurgical instrument. The torque limiting mechanism generally includes adriven member, engageable with an approximating mechanism of thesurgical instrument, and having a driven surface; and a driving memberhaving a driving surface engageable with the driven surface of thedriven member. The driving member is connected to the clamping actuatorof the instrument. The driving surface of the driving member slipsrelative to the driven surface of the driven member at a predeterminedengagement pressure. The mechanism has a torque control with a memberthat adjusts the pressure applied by the driving member to the drivenmember.

In certain preferred embodiments, the driving member is rotatablerelative to the driven member. The driving surface can frictionallyengage the driven surface. In certain embodiments, the driving surfaceand the driven surface have interengaging structure. In a specificembodiment, the driving surface and the driven surface haveinterengaging teeth.

In a further alternative embodiment, the interengaging structure is adetent mechanism. The detent mechanism includes at least one movableconnector positioned between the driving surface and the driven surface.In a more specific embodiment, at least one of the driving surface anddriven surface includes cups and the other of the driving surface anddriven surface supports balls removably engageable with the cups.

The disclosed torque limiting mechanism further includes a springengageable with the driving member such that the driving member isspring biased into engagement with the driven member.

A torque control is provided and is engageable with the biasing springto preset the amount of pressure applied by the biasing spring to thedriving member. The torque control includes a hook engageable with thebiasing spring and a slide member.

There is also provided a surgical instrument including a body portion, afirst clamping member mounted on the body portion and a second clampingmember movable relative to the first clamping member. An approximatingmechanism is provided for moving the second clamping member relative tothe first clamping member. The approximating mechanism includes alongitudinally movable drive screw having a helical groove formedtherein and a rotatable sleeve mounted about the drive screw. Therotatable sleeve includes a drive pin extending into the helical groovesuch that rotation of the rotatable sleeve longitudinally translates thedrive screw within the body portion.

A torque limiting mechanism is provided within the body portion and isengageable with the rotatable sleeve such that at least a portion of thetorque limiting mechanism slips relative to the rotatable sleeve at apredetermined engagement pressure. The torque limiting mechanismincludes a driven surface affixed to the rotatable sleeve and a drivingsurface engageable with the driven surface.

In one embodiment, the driving surface frictionally engages the drivensurface. In an alternative embodiment, the driving surface and thedriven surface have interengaging structure. In a specific embodiment,the driving surface and the driven surface have interengaging teeth.

In a further alternative embodiment, the interengaging structure is adetent mechanism, wherein at least one of the driving surface and drivensurface includes cups and the other of the driving surface and drivensurface supports balls removably engageable with the cups.

The surgical instrument further includes a spring engageable with thedriving member. The driving member is spring biased into engagement withthe driven member.

There is further disclosed a method of preventing over compression oftissue between first and second clamping members of a surgicalinstrument. The method includes providing a surgical instrument having abody portion, a first clamping member mounted on the body portion and asecond clamping member movable relative to the first clamping member. Anapproximating mechanism is provided for moving the second clampingmember relative to the first clamping member. The approximatingmechanism includes a longitudinally movable drive screw having a helicalgroove formed therein and a rotatable sleeve mounted about the drivescrew.

The rotatable sleeve includes a drive pin extending into the helicalgroove such that rotation of the rotatable sleeve longitudinallytranslates the drive screw within the body portion. A torque limitingmechanism is provided and is engageable with the rotatable sleeve. Anapproximation knob is rotationally mounted on the body portion and isengagable with the torque limiting mechanism.

The method further includes the step of rotating the approximation knobto rotate rotatable sleeve such that at least a portion of the torquelimiting mechanism slips relative to the rotatable sleeve at apredetermined engagement pressure.

DESCRIPTION OF THE DRAWINGS

Various embodiments of the presently disclosed surgical stapler with atorque limiting mechanism for controlled tissue compression aredisclosed herein with reference to the drawings, wherein:

FIG. 1 is a perspective view of a surgical stapler incorporating oneembodiment of a torque limiting mechanism for controlled tissuecompression;

FIG. 2 is a perspective view, with parts separated, of a handle portionof the surgical stapler of FIG. 1;

FIG. 3 is a perspective view, with parts separated, of a torque limitingmechanism utilized in the handle portion of FIG. 2;

FIG. 4 is a perspective view of the torque limiting mechanism of FIG. 3;

FIG. 5 is a side view of the torque limiting mechanism of FIG. 4 withfriction or pressure plates engaged;

FIG. 6 is a side view similar to FIG. 5 with the friction platesslipping relative to each other;

FIG. 7 is a perspective view of an alternative embodiment of a torquelimiting mechanism for use in the surgical stapler of FIG. 1;

FIG. 8 is a side view of the torque limiting mechanism of FIG. 7 with adriven plate and drive plate engaged;

FIG. 9 is a view similar to FIG. 8 with the drive and driven platesdisengaged;

FIG. 10 is a perspective view of a further alternative embodiment of atorque limiting mechanism for use with the surgical stapler of FIG. 1;

FIG. 11 is a side view of the torque limiting mechanism of FIG. 10 witha driven plate and drive plate engaged; and

FIG. 12 is a view similar to FIG. 11 with the drive and driven platesdisengaged.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the presently disclosed surgical stapling deviceincorporating tissue compression limiting mechanisms will now bedescribed in detail with reference to the drawings wherein like numeralsdesignate identical or corresponding elements in each of the severalviews. As is common in the art, the term ‘proximal” refers to that partor component closer to the user or operator, i.e. surgeon or physician,while the term “distal” refers to that part or component further awayfrom the user.

Referring initially to FIG. 1 there is disclosed a surgical staplingdevice 10. Surgical stapling device 10 is a circular stapler. Surgicalstapling device 10 generally includes a handle assembly 12 and anelongate body portion 14 extending distally from handle assembly 12. Anoperable head assembly 16 is mounted on a distal end 18 of elongate bodyportion 14 and generally includes a staple cartridge 20 mounted todistal end 18 of elongate body portion 14 and an anvil assembly 22 whichis movable relative to staple cartridge 20 in a manner described in moredetail hereinbelow. Anvil assembly 22 includes an anvil plate 24 and ananvil shaft 26 extending proximally from anvil plate 24. A movable anvilretainer or retention shaft 28 extends out of distal end 18 of elongatebody portion 14 and is provided to removably receive anvil shaft 26. Anapproximation knob 30 is rotatably mounted on a body housing 32 ofhandle assembly 12 and is operable to move anvil assembly 22 relative tostaple cartridge 20 to grasp and compress tissue.

A trigger 34 is movably mounted to a trigger extension 36 of bodyhousing 32. Actuation of trigger 34 functions to eject staples (notshown) out of staple cartridge 20 and into anvil plate 24. A triggerlock 38 is movably mounted on body housing 32 and is provided to blockmovement of trigger 34 until manually moved out of the way of trigger 34to prevent inadvertent firing. The handle assembly and body housing maybe arranged as disclosed in U.S. Pat. No. 7,303,106, the disclosure ofwhich is hereby incorporated by reference herein, in its entirety. The'106 patent also discloses an assembly having a pusher back 186, acylindrical knife 188 and a staple guide 192. The pusher back isconnected to a pusher link 74 and has a plurality of pusher fingers forfiring the surgical staples from the staple cartridge.

A torque limiting mechanism 40 is contained within body housing 32 tocontrol the amount of compression applied to tissues captured betweenstaple cartridge 20 and anvil plate 24. Approximation knob 30 isengageable with torque limiting mechanism 40 such that when tissuescompressed between staple cartridge 20 and anvil plate 24 reach apredetermined level of compression, approximation knob 30 slips free ofengagement with anvil retention shaft 28 thereby preventing any furthercompression to the tissue. Torque limiting mechanism 40 includes atorque control 42, extending through body housing 32, for presetting thelevel at which approximation knob 30 slips in a manner describedhereinbelow. An indicia plate 44 is mounted on body housing 32 adjacenttorque control 42 and includes numerical indicia 46 to allow theoperator to preset the slip point or range of approximation knob 30. Inthis way, the experience of the surgeon can be used to set theinstrument according to the type of tissue being stapled or clamped, theage of the patient, the condition of the tissue, or other factors.

Referring now to FIGS. 1 and 2, in order to move anvil assembly 22relative to staple cartridge 20 in response to rotation of approximationknob 30 (FIG. 1), surgical stapling instrument 10 includes a drive screw48 and a rotatable sleeve 50 mounted in body housing 32 of handleassembly 12. Drive screw 48 is longitudinally movable within bodyhousing 32 and is connected to anvil retention shaft 28. Drive screw 48includes a pin 52, positioned through a distal end 54 of drive screw 48,which is directly or indirectly connected to the anvil retention shaft28 in a known manner. For example, in order to transmit longitudinalmotion through curved elongate body portion 14, pin 52 may be connectedto proximal ends of bands (not shown) while distal ends of the bands maybe connected to anvil retention shaft 28 in a manner described in moredetail in U.S. Pat. No. 7,303,106, the disclosure of which is herebyincorporated by reference herein. Thus, longitudinal movement of drivescrew 48 within body housing 32 effects longitudinal movement of anvilassembly 22 relative to staple cartridge 20.

As shown, body housing 32 is provided as complementary halves 32 a and32 b. A seal 56 is provided in a circumferential groove 58 formed indistal end 54 of drive screw to prevent escape of insuffflation gasesand other fluids through elongate body portion 14 and out body housing32. A screw stop 64 is provided on distal end 54 of drive screw 48 tolimit the longitudinal travel of drive screw 48 within body housing 32.A helical groove 60 is provided in a proximal portion 62 of drive screw48 and is engaged by rotatable sleeve 50 in order to move drive screw 48longitudinally.

Specifically, drive screw 48 is positioned within a bore 66 formedwithin rotatable sleeve 50. An enlarged collar 68 rotatably supportsrotatable sleeve 50 within body housing 32. In order to move drive screw48 longitudinally within bore 66 of rotatable sleeve 50, a drive pin 70extends through a hole 72 formed through enlarged collar 68 and extendsinto bore 66. Drive pin 70 rides within helical groove 60 formed inproximal portion 62 of drive screw 48. Thus, as rotatable sleeve 50 isrotated within body housing 32, drive pin 70 rides within helical groove62 drawing and/or advancing drive screw 48 within body housing 32. Asnoted herein above, drive screw 48 is connected to anvil assembly 22.Longitudinal movement of drive screw 48 within body housing 32 effectslongitudinal movement of anvil assembly 22 relative to staple cartridge20.

As approximation knob 30 is rotated, rotational force or torque isapplied to rotatable sleeve 50 to rotate rotatable sleeve 50 and movedrive pin 70 within helical groove 60 in drive screw 48. The rotationalforce is converted to longitudinal or linear force moving anvil assembly22 toward staple cartridge 20 thereby compressing tissue capturedbetween anvil and staple cartridge in response to rotation ofapproximation knob 30.

In the absence of any control or limiting factors, as continued torqueis applied to rotatable sleeve 50, an increasing amount of linear forceis transmitted to, or exerted on, anvil assembly 22 thereby applying anincreasing amount of compression to the tissue captured between anvilplate 24 of anvil assembly 22 and staple cartridge 20. In order toprevent over compression or under compression, torque limiting mechanism40 is provided to limit the amount of torque applied to rotatable sleeve50, and thus the amount of linear force applied to anvil assembly 22, toa predetermined or adjustable level.

Referring now to FIGS. 2 and 3, enlarged collar 68, which supportsrotatable sleeve 50 within body housing 32 (FIG. 2) is located at adistal end 74 of rotatable sleeve 50. In order for the surgeon tomanually rotate rotatable sleeve 50, a proximal end 76 of rotatablesleeve 50 is provided with a driven member or disk 78 having a drivensurface 80. Driven disk 78 forms a part of torque limiting mechanism 40.As noted herein above, approximation knob 30 is provided on body housing32 and is rotatable to affect movement of anvil assembly 22. As shown,torque limiting mechanism 40 is located between approximation knob 30and rotatable sleeve 50. Torque limiting mechanism 40 is provided tolimit the amount of rotational torque applied to rotatable sleeve 50 inorder to control the amount of linear force, and thus tissuecompression, applied to anvil assembly 22.

Referring to FIGS. 2, 3 and 4, in this embodiment, torque limitingmechanism 40 further includes a driving member or disk 82 having adriving surface 84. Driving surface 84 is provided to fictionally engagedriven surface 80 of driven disk 78 in order to rotate rotatable sleeve50. The driving member or disk 82 is also attached to the knob 30.Driving disk 82 is mounted on a drive shaft 86. Drive shaft 86 includesa support disk 88 provided at a distal end 90 of driveshaft 86. Supportdisk 88 is rotatably supported within a circumferential groove 92 formedin rotatable sleeve 50 (FIGS. 3 and 4). A proximal end 94 of driveshaft86 is affixed to approximation knob 30. Specifically, proximal end 94 ofdrive shaft 86 is fixed within a hole 96 formed in approximation knob30. Therefore, as approximation knob 30 is rotated, driving disk 82 oftorque limiting mechanism 40 frictionally engages and rotates drivendisk 78 of torque limiting mechanism 40 provided on rotatable sleeve 50.

Torque limiting mechanism 40 further includes a biasing spring 98 whichis provided between approximation knob 30 and driving disk 82 to biasdriving disk 82 into frictional engagement with driven disk 78. Driveshaft 86 extends through a hole 100 in driving disk 82. While notspecifically shown, driving disk 82 is keyed (such as with a pin) orotherwise mounted on drive shaft 86 such that driving disk 82 rotateswith drive shaft 86 and is free to move longitudinally along drive shaft86 in order to disengage from or slipped relative to driven disk 78.

As noted herein above, torque control 42 (FIGS. 1 and 2) is provided onbody housing 32 to adjustably control the amount of compressive forcesapplied to tissue between staple cartridge 20 and anvil assembly 22.Referring for the moment to FIG. 2, torque control 42 includes a slide102 which may be manually graspable and extend outside of body housing32 to be located adjacent indicia plate 44. A member or hook 104 extendsfrom slide 102 and engages coils such as, for example, coils 106, 108,etc., of biasing spring 98 to adjust the amount of spring pressureapplied to driving disk 82. The torque control 42 adjusts the pressureapplied by the driving member to the driven member. In this manner,torque control 42 is able to preset the maximum amount of pressureapplied to driven member or disk 78 by driving member or disk 82. Thispre-sets a maximum amount of torque to be applied to rotatable sleeve 50and thus the maximum amount of compressive forces to be applied totissue captured between staple cartridge 20 and anvil assembly 22.

It should be noted that, while torque limiting mechanism 40 includes abiasing spring 98 to bias driving disk 82 into engagement with drivendisk 78, torque limiting mechanism 40 may omit biasing spring 98. Inthis configuration, driven surface 80 of driven disk 78 and drivingsurface 84 of driving disk 82 may be manufactured with predeterminedcoefficients of friction such that driving disk 82 slips relative todriven disk 78 at a predetermined torque limit.

Referring now to FIGS. 1, 2, 5 and 6, the use of torque limitingmechanism 40 to limit the amount of rotational force or torque appliedto rotatable sleeve 50 will now be described. Referring initially toFIGS. 1 and 2, torque control 42 is adjusted such that hook 104 appliesthe desired amount of preload pressure to biasing spring 98. This isaccomplished by a sliding slide 102 relative to indicia plate 44 untilslide 102 is aligned with the appropriate numerical indicia 46 onindicia plate 44. Thereafter, approximation knob 30 is rotated in thedirection of arrow A (FIG. 5) to draw anvil assembly 22 toward staplecartridge 20 thereby compressing first and second tissue sections T1 andT2 together and bring the tissue sections into position to be stapled.

Referring specifically to FIG. 5, rotation of approximation knob 30 inthe direction of arrow A rotates driving disk 82 in the direction ofarrow B. Driving disk 82's frictional engagement with driven disk 70rotates driven disk 78 in the direction of arrow C thereby rotatingrotatable sleeve 50 to compress the tissue sections as describedhereinabove.

Referring now to FIG. 6, as approximation knob 30 continues to berotated, the increasing compression of first and second tissue sectionsT1 and T2 requires an increasing amount of linear force passing throughdrive screw 48 and thus an increasing amount of rotational torquerequired by rotatable sleeve 50. At the predetermined amount of pressureapplied by biasing spring 98 and controlled by torque control 42, thefrictional forces between driven disk 78 and driving disk 82 areovercome allowing driving disk 82 to slip relative to driven disk 78. Asdriving disk 82 slips relative to driven disk 78, no further increasingamount of torque is applied to rotatable sleeve 50 and thus no furtherincreasing amount of linear force is transmitted through drive screw 48to anvil assembly 22. In this manner, torque limiting mechanism 40prevent over compression of tissues captured between anvil assembly 22and staple cartridge 20.

Referring now to FIGS. 7-9, and initially with regard to FIG. 7, thereis disclosed an alternative embodiment of a torque limiting mechanism110 for use with surgical stapling device 10 described herein above.Similar to torque limiting mechanism 40 described above, torque limitingmechanism 110 generally includes a driven member or disk 112 provided onproximal end 76 of rotatable sleeve 50 and a driving member or disk 114mounted for longitudinal movement along a driveshaft 116. A biasingspring 118 is provided around drive shaft 116 and biases driving disk114 into engagement with driven disk 112. Similar to driving disk 82described herein above, driving disk 114 is mounted for rotationalmovement along with drive shaft 116 and is free to move longitudinallyalong drive shaft 116 against the bias of biasing spring 118.

A support disc 120 is provided on a distal end 122 of drive shaft 116and is rotatably supported within circumferential groove 92 in rotatablesleeve 50. A proximal end 124 of drive shaft 116 is affixed within hole96 in approximation knob 30. Thus, rotation of approximation knob 30rotates drive shaft 116 and thus driving disk 114. In this embodiment,driven disk 112 is provided with a plurality of pawls or driven diskteeth 126 which are mechanically interengageable with a plurality ofcorresponding pawls or driving disk teeth 128 formed on driving disk114. Driven disk teeth 126 and driving disk teeth 128 form respectivedriven and driving surfaces 130 and 132 on driven disk 112 and drivingdisk 114.

Referring now to FIGS. 8 and 9, in use, biasing spring 118 biasesdriving disk 114 into engagement with driven disk 112. Specifically,biasing spring 118 biases driving surface 132, including driving teeth128, into engagement with driven surface 130, including driven teeth126. In a manner identical to that described herein above, torquecontrol 42 is manipulated to adjust the maximum amount of force appliedby biasing spring 118 to driving disk 114. As approximation knob 30 isrotated, driving teeth 128 on driving disk 114 are interengaged withdriven teeth 126 on driven disk 112 to thereby rotate rotatable sleeve50. As further noted herein above, rotation of rotatable sleeve 50effects longitudinal movement of anvil assembly 22 relative to staplecartridge 20 to thereby compress tissue.

With specific reference to FIG. 9, as rotatable sleeve 50 is rotated, anincreasing amount of force is required to continue to rotate rotatablesleeve 50 due to the compressive forces existing between the tissues.Continued rotation of approximation knob 30 continues to apply torquedto rotatable sleeve 50 until such time as the amount of torque requiredexceeds the pressure applied to driving disk 114 by biasing spring 118.At this point, driving disk 114 “slips” relative to driving disk 112 andmoves proximally in the direction of arrow D against the bias of biasingspring 118. Specifically, driving teeth 128 on driving disk 114 sliprelative to or are disengaged from driven teeth 126 on driven disk 112thereby preventing any further application of increased torque torotatable sleeve 50. In this manner, torque limiting mechanism 110prevents over compression of tissues captured between anvil assembly 22and staple cartridge 20.

Referring now to FIGS. 10-12, and initially with regard to FIG. 10,there is disclosed a further alternative embodiment of a torque limitingmechanism 140 for use with surgical stapling device 10. Similar totorque limiting mechanism 40 described above, torque limiting mechanism140 generally includes a driven member or disk 142 provided on proximalend 76 of rotatable sleeve 50 and a cone shaped driving member or disk144 mounted for longitudinal movement along a drive shaft 146. A biasingspring 148 is provided around drive shaft 146 and biases driving disk144 into engagement with driven disk 142. Similar to driving disk 82described herein above, driving disk 144 is mounted for rotationalmovement along with drive shaft 146 and is free to move longitudinallyalong drive shaft 146 against the bias of biasing spring 148.

A support disc 150 is provided on a distal end 152 of drive shaft 146and is rotatably supported within circumferential groove 92 in rotatablesleeve 50. A proximal end 154 of driveshaft 146 is affixed within hole96 in approximation knob 30. Thus, rotation of approximation knob 30rotates drive shaft 146 and thus driving disk 144. In this embodiment,driven disk 142 includes a driven disk surface 156 and driving disk 144includes a driving disk surface 158. At least one releasable connector160 is provided between driven disk surface 156 and driving disk surface158. Releasable connector 160 slips relative to driven disk surface 156and\or driving disk surface 158 when a preset amount of torque isapplied to rotatable sleeve 50.

In this specific embodiment, releasable connectors 160 are in the formof a plurality of connecting balls 162. Driven disk surface 156 ofdriven disk 142 includes a plurality of driven disk cups 164 and drivingdisk surface 158 of driving disk 144 includes a plurality ofcorresponding driving disk cups 166. Connecting balls 162 are movablysupported between driven disk cups 164 and driving disk cups 166.Connecting balls 162 are maintained between driving disk cups 164 anddriven disk cups 166 by the biasing pressure of biasing spring 148 ondriving disk 144.

Referring now to FIGS. 11 and 12, in use, approximation knob 30 isrotated such that driving disk 144 rotates driven disk 142 throughconnecting balls 162. Rotation of driven disk 142 correspondinglyrotates rotatable sleeve 50 thereby effecting longitudinal movementbetween anvil assembly 22 and staple cartridge 20 (FIG. 1). As anvilassembly 22 moves towards staple cartridge 20 to compress the tissuesthere between, an increasing amount of rotational force or torque isrequired to be applied to rotatable sleeve 50.

As best shown in FIG. 12, an increasing amount of rotational force isrequired to be applied to approximation knob 30 to continue rotation ofrotatable sleeve 50. When the force needed to continue rotation arotatable sleeve 50 exceeds that preset by torque control 42, drivingdisk 144 moves proximally against the bias of biasing spring 148. Thiscauses connecting balls 162 to slit or “pop” out of driving disk cups166 thereby removing any further rotational force applied to driven disk142. Alternatively, while not specifically shown, connecting balls 162may be firmly affixed within driving disk cups 166 in driving disk 144such that releasable connecting balls 162 slip or pop out of driven diskcups 164 in driven disk 142 as driving disk 144 moved proximally againstthe pressure of biasing spring 140. In this manner, torque limitingmechanism 140 prevents over compression of tissues captured betweenanvil assembly 22 and staple cartridge 20 of surgical stapling device10.

In further embodiments of the present disclosure, the body housing andhandle assembly can incorporate a motorized actuator and may beconnected to, or incorporate therein, a power source. An example of apowered, motorized device is disclosed in International Publication No.WO 09/039506 and U.S. Pat. No. 7,032,798, the disclosures of which arehereby incorporated by reference herein, in their entirety. The manuallypowered device discussed above converts the pivoting motion of thehandle into linear motion of the anvil retention shaft. A motorizeddevice can generate rotational motion, which is then converted to linearmotion for clamping tissue, firing staples, and/or cutting tissue.

It will be understood that various modifications may be made to theembodiments disclosed herein. For example, alternative disconnectingmechanisms may be provided such as, for example, multiple frictionplates, magnetic engagement mechanisms, etc. Further, the disclosedtorque limiting mechanisms may find application in any surgicalinstrumentation incorporating tissue compression structure.Additionally, the disclosed torque limiting mechanisms may be providedas modular and interchangeable components having differing ranges ofengagement pressures for use in surgical instruments. In addition, oneor more removable adapters having an elongate shaft extending from thehandle assembly to the distal end of the device can be used. Suchadapters can have flexible shafts, curved, or other shapes, and may bedesigned to connect to various end effectors. Such adapters can also bedesigned to be connected to a manually driven handle assembly, amotorized actuator, or both. An adapter is disclosed in U.S. Pat. No.7,922,063, the disclosure of which is hereby incorporated by referenceherein, in its entirety. Therefore, the above description should not beconstrued as limiting, but merely as exemplifications of particularembodiments. Those skilled in the art will envision other modificationswithin the scope and spirit of the claims appended hereto.

The invention claimed is:
 1. A surgical instrument comprising: a bodyportion; a first clamping member mounted on the body portion and asecond clamping member movable relative to the first clamping member; anapproximating mechanism for moving the second clamping member relativeto the first clamping member, the approximating mechanism including alongitudinally movable drive screw having a helical groove formedtherein and a rotatable sleeve mounted about the drive screw, therotatable sleeve including a drive pin extending into the helical groovesuch that rotation of the rotatable sleeve longitudinally translates thedrive screw within the body portion; and a torque limiting mechanismengagable with the rotatable sleeve, the torque limiting mechanismincluding: a driven surface coupled with the rotatable sleeve; a drivingsurface engagable with the driven surface; a spring configured to biasthe driving surface towards the driven surface; and a slider configuredto selectively engage coils of the spring to selectively adjust thebiasing force applied to the driving surface, wherein driving surface isconfigured to slip relative to the the driven surface at a predeterminedengagement pressure.
 2. The surgical instrument as recited in claim 1,wherein the driving surface frictionally engages the driven surface. 3.The surgical instrument as recited in claim 1, wherein the drivingsurface and the driven surface have interengaging structure.
 4. Thesurgical instrument as recited in claim 3, wherein the driving surfaceand the driven surface have interengaging teeth.
 5. The surgicalinstrument as recited in claim 3, wherein the interengaging structure isa detent mechanism.
 6. The surgical instrument as recited in claim 5,wherein at least one of the driving surface and driven surface includescups and the other of the driving surface and driven surface supportsballs removably engageable with the cups.
 7. The surgical instrument asrecited in claim 1, wherein the slider includes a hook configured toselectively engage the coils of the spring.
 8. The surgical instrumentas recited in claim 7, wherein the slider is slidably disposed withrespect to the body portion such that translation of the slider causesthe hook to engage at least one of the coils.